"So many investors have lost so rapidly so much," said Galvin. "We intend to move quickly. We need to get answers for average American investors."
A spokesman for Morgan Stanley provided a statement saying the bank "followed the same procedures for the Facebook offering that it follows for all IPOs."
"After Facebook released a revised S-1 filing on May 9th providing additional guidance with respect to business trends, a copy of the amendment was forwarded to all of MS's institutional and retail investors and the amendment was widely publicized in the press at the time," Morgan Stanley said.
In response to the information about business trends, a significant number of research analysts in the syndicate who were participating in investor education reduced their earnings views to reflect their estimate of the impact of the new information. These revised views were taken into account in the pricing of the IPO."
A spokeswoman for JP Morgan Chase, one of the underwriters, declined to comment about the class action lawsuit.
ABC News' Emily Chang, Lauren Pearle and Jason Volack contributed to this report.